I would put a dummy comment inside the script tag. so
instead of <script src="foo.js"/> say
<script src="foo.js"><!-- placeholder--></script>
because that will avoid the serializer or browser being misled
by an empty element.
I don't pretend to understand why your thing doesn't work,
but if this solves it, at least you can move on.
--
Sebastian Rahtz
Director (Research) of Academic IT
University of Oxford IT Services
13 Banbury Road, Oxford OX2 6NN. Phone +44 1865 283431